GLYCEROL FORMAL: Injectable Pharmaceutical Formulations

The pharmaceutical industry continues to develop increasingly complex active pharmaceutical ingredients (APIs), many of which exhibit poor aqueous solubility. While these molecules often demonstrate excellent therapeutic efficacy, their limited solubility presents significant formulation challenges for injectable dosage forms.

Glycerol Formal emerged as a valuable co-solvent in pharmaceutical formulation research due to its excellent solvency, water miscibility, relatively low volatility, and compatibility with a broad range of pharmaceutical ingredients. When appropriately formulated and evaluated, the Glycerol Formal can assist formulation scientists in increasing API solubility, reducing precipitation, and improving formulation stability for selected parenteral applications.

CAS: 4740-78-7 & 5464-28-8

EC NUMBER: 911-694-8

IUPAC: 1,3-Dioxan-5-ol & 1,3-Dioxolan-4-ylmethanol

Other terms: α,α′-Glycerol formal

Molecular Formula: 2(C₄H₈O₃)

Appearance: Clear colourless liquid

Appearance: Odourless

Boiling Point (°C) at 1013 hPa193.95
Flash point (°C) at 1013 hPa [DIN 51755 part 2, closed cup]99
Vapour pressure (kPa) at 20°C [ASTM D323 modified]0.03
Evaporation rate [ASTM D3539, Butyl acetate =1]0.041
Relative density at 20°C [OECD 109]1.218
Surface tension (mN/m) at 25°C44.49
Water solubility (g/L) at 20°CFully miscible
Kinematic viscosity (mm²/s) at 25°C11.7
Hansen Solubility parameters (MPa^(1/2))Total (δT): 26.07
Dispersion (δd): 18.2
Polarity (δp): 10.1
Hydrogen bond (δh): 15.7

KEY FEATURES

  • Broad Solvency for Poorly Soluble APIs

    Many new chemical entities (NCEs) exhibit low water solubility. Glycerol Formal can improve the dissolution of certain lipophilic or moderately polar drug molecules, enabling higher drug loading and reducing the need for multiple co-solvents. This capability is particularly valuable during early-stage formulation screening, where researchers evaluate solvent systems capable of maintaining drug stability while achieving clinically relevant concentrations.

  • Complete Water Miscibility

    Glycerol Formal is fully miscible with water, allowing formulators to prepare solvent systems that combine organic solvency with aqueous compatibility. This facilitates the development of mixed-solvent systems where water, Glycerol Formal, and additional pharmaceutical excipients work together to achieve target solubility and stability.

  • Controlled Evaporation During Manufacturing

    Compared with highly volatile organic solvents, Glycerol Formal exhibits a relatively high boiling point and low vapor pressure. During pharmaceutical manufacturing, these characteristics may contribute to:

    • Improved processing consistency
    • Reduced solvent evaporation
    • Better batch reproducibility
    • Lower operator exposure

  • Compatibility with Multi-Component Solvent Systems

    Glycerol Formal is often evaluated alongside commonly used pharmaceutical co-solvents such as:

    By combining complementary solvent properties, formulators can optimize API solubility while balancing viscosity, osmolality, and injection performance.

APPLICATIONS

  • Solubilizing Poorly Water-Soluble APIs
    One of the principal applications of Glycerol Formal is increasing the apparent solubility of hydrophobic drug candidates. This enables researchers to formulate compounds that would otherwise be difficult to administer as injectable products.
  • Veterinary Injectable Medicines
    Veterinary pharmaceuticals frequently contain highly lipophilic active ingredients requiring specialized solvent systems. Glycerol Formal has been investigated as a component of solvent blends for selected veterinary injectable formulations where enhanced drug loading and stability are required.

  • Long-Acting Injectable Formulations
    Controlled-release injectables continue to expand in areas such as endocrinology, psychiatry, oncology, and animal health. Although formulation strategies vary, solvent selection plays an important role in determining:

    • Drug release profile
    • Depot formation
    • Injection characteristics
    • Stability during storage

    Glycerol Formal may be evaluated as part of these advanced formulation systems where appropriate.

  • Research and Development
    During pharmaceutical R&D, formulation scientists routinely screen numerous solvent combinations before selecting the optimal composition for further development. Glycerol Formal provides an additional option for scientists investigating:

    • Solubility enhancement
    • Excipient compatibility
    • Prototype formulations
    • Stability optimization

F. A. Q.

It is investigated as a co-solvent to enhance the solubility of poorly water-soluble APIs, improve formulation stability, and support development of specialized solvent systems.

Glycerol Formal demonstrates strong solvency for many hydrophobic and moderately polar compounds, making it useful during formulation screening. However, suitability must be confirmed experimentally for each API.

Typically not, it is commonly evaluated as one component of a mixed solvent system with water and other pharmaceutical excipients to achieve the desired balance of solubility, viscosity, and stability.

Its primary role is to facilitate formulation by increasing drug solubility. Improved solubility may contribute to better delivery of certain APIs, but overall bioavailability depends on many factors beyond the solvent itself.

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